Is it safe to run an amp with no power tubes?

[Turd Ferguson]

As the thread title says...

The Background
I have several heads, all with reactive load boxes, no speakers connected. The FX send of each amp goes to a rack mixer -> FX -> 6L6 power amp -> cabs.

The Dilemma
I’m kind of tempted to get another amp (because why not) that I would add to the setup in the same fashion. But I already have 4 load boxes and don’t want to buy another.

The Potentially Dumb Idea
Can I just remove the power tubes from an amp and use it as a preamp, without a load box/speaker? Does this effectively “turn off” the power amp/output transformers?

I know this is done for diagnostic purposes, but I’m too dumb to know if it’s safe long term.

 

[MaxOfMetal]

It depends a lot on the amp, more specifically how the power amp is layed out, but usually no it's not safe.

 

[MatrixClaw]

Are you using all 4 amps at the same time? Why not buy a head switcher that puts a load on all the amps not being used? That seems a lot cheaper than having a reactive loadbox for each one.

 

[Turd Ferguson]

Are you using all 4 amps at the same time? Why not buy a head switcher that puts a load on all the amps not being used? That seems a lot cheaper than having a reactive loadbox for each one.

No I just plug into whichever amp I feel like playing at any given time. I've looked at those amp switchers though, and they're pretty expensive. Two of my load boxes were used Two Notes Captors I got fairly cheap, and two I bought new, so I don't feel too bad about that expense. But I'm reluctant to buy more, that's for sure. I could always just swap one around. I'm just lazy.

 

[SalsaWood]

Even amps with dedicated pre outputs still need a cab load AFAIK. I am hard pressed to think of any amp where this isn't the case.

Radial switchers are great, I've used them in the past. For a no-hassle solution they're worth the money.

 

[Turd Ferguson]

Even amps with dedicated pre outputs still need a cab load AFAIK. I am hard pressed to think of any amp where this isn't the case.

Radial switchers are great, I've used them in the past. For a no-hassle solution they're worth the money.

Yes I'm sure I still need a load...except for the Mark V:25, it has a speaker out disable switch. I was just curious if removing the power tubes would effectively "turn off" the power amp section.

 

[TheWarAgainstTime]

Yes I'm sure I still need a load...except for the Mark V:25, it has a speaker out disable switch. I was just curious if removing the power tubes would effectively "turn off" the power amp section.

Since you're running the FX sends to your mixer/power amp, you wouldn't have to do anything else with the V:25 head besides switching off the speaker output on the back panel. The amp sees the internal load, and the power section gets no signal since there's nothing coming back through the FX return.

 

[NickK-UK]

Usually the amp power goes Power Transformer => Power tubes -> preamp tubes. The power tubes provide a certain amount of current draw - this usually reduces the B+ voltages. If you remove them then the B+ will rise. If the components are close to their voltage rating then you could find they fail and that may destroy other things in the amp.

If the amp is a Push Pull then you will need to balance the power tubes if you run with less power tubes otherwise you'll get higher DC and could end up running unsaturation causing the output transformer a problem or causing it to fail.

The impact depends on the design.

 

[Turd Ferguson]

Since you're running the FX sends to your mixer/power amp, you wouldn't have to do anything else with the V:25 head besides switching off the speaker output on the back panel. The amp sees the internal load, and the power section gets no signal since there's nothing coming back through the FX return.

Yeah, I just keep a Captor on there because I'm afraid of accidentally flipping that switch to the wrong position.

 

[Turd Ferguson]

Usually the amp power goes Power Transformer => Power tubes -> preamp tubes. The power tubes provide a certain amount of current draw - this usually reduces the B+ voltages. If you remove them then the B+ will rise. If the components are close to their voltage rating then you could find they fail and that may destroy other things in the amp.

If the amp is a Push Pull then you will need to balance the power tubes if you run with less power tubes otherwise you'll get higher DC and could end up running unsaturation causing the output transformer a problem or causing it to fail.

The impact depends on the design.

Interesting. I knew someone here would have an in-depth understanding. Thank you.

I found it interesting that of all my amps, the DSL 20 is the only one that has signal at the FX send when the standby switch is off.

 

[MatrixClaw]

No I just plug into whichever amp I feel like playing at any given time. I've looked at those amp switchers though, and they're pretty expensive. Two of my load boxes were used Two Notes Captors I got fairly cheap, and two I bought new, so I don't feel too bad about that expense. But I'm reluctant to buy more, that's for sure. I could always just swap one around. I'm just lazy.

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I bought mine for $400 on Reverb.

 

[SpinalTap]

Sell all your amps and get a quad cortex

 

[Turd Ferguson]

Sell all your amps and get a quad cortex

I have been tempted to go the Fractal route TBH...

 

[technomancer]

I have been tempted to go the Fractal route TBH...

Been there done that and you've seen where I'm at now

 

[cwhitey2]

One of the only amps I think of that kinda do what you are talking about is a Fryette cl100 (other Fryettes might do it as well). There is a switch to turn off the power section to access only the preamp. The switch is called "POWER AMP MODE: MUTE".

 

[melomanic]

 

[budda]

Been there done that and you've seen where I'm at now

Thats because you like modding irl and shiny things.

I have real amps and an axefx, have both

 

[Voodoo Marshall]

I ran my 50W JCM 800 no tubes for awhile using it as the pre-amp to a stereo set up (Peavy stereo tube amp). It was modded with a preamp out. No problems. Back to simple set up now with tubes in.

 

[Elric]

As the thread title says...

The Background
I have several heads, all with reactive load boxes, no speakers connected. The FX send of each amp goes to a rack mixer -> FX -> 6L6 power amp -> cabs.

The Dilemma
I’m kind of tempted to get another amp (because why not) that I would add to the setup in the same fashion. But I already have 4 load boxes and don’t want to buy another.

The Potentially Dumb Idea
Can I just remove the power tubes from an amp and use it as a preamp, without a load box/speaker? Does this effectively “turn off” the power amp/output transformers?

I know this is done for diagnostic purposes, but I’m too dumb to know if it’s safe long term.

Get a real amp switcher. If you are going to collect amps it is worth it. My amp switcher literally paid for itself on arrival because I could sell a bunch of load boxes and other gear that was redundant across all the different heads I had. It also allows me to redirect any head I have to any cab I have on the fly. It is literally life changing.

 

[Turd Ferguson]

Appreciate all the input guys. I've looked into amp switchers in the past, might have to re-visit that. Or just stop being lazy and swap reactive loads from amp to amp. I only play one at a time anyway. Thing that scares me about that is what if I turn one on and forget the load.

Or maybe I just shouldn't buy any more amps.









Who am I shitting. I'm gonna end up buying more amps.